1. Field of the Invention
The present invention relates to a module board. More particularly, the present invention relates to, for example, a module board of a circuit module or the like in which a sealing resin is covered with a shield layer. The sealing resin is formed so as to seal an electronic component mounted on one of the principal surfaces of a base substrate.
2. Description of the Related Art
An example of a circuit module of a related art, serving as a background of the invention, is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 2004-172176 (Patent Document 1). The circuit module disclosed in Patent Document 1 is one in which a component that is disposed on a substrate is covered with an insulating layer. This circuit module includes a shield layer connected to a ground electrode provided on the substrate. In the circuit module, the shield layer is formed of a conductive resin and, in general, a filler, such as Ag or Cu, is used as a conductive component of the conductive resin.
As in the circuit module that is disclosed in Patent Document 1, the shield layer using a filler, such as Ag or Cu, provides good shield characteristics with respect to external interfering waves. However, the shield layer interferes with the component disposed on the substrate and causes the circuit module characteristics to be deteriorated. An example of such a case is when the shield layer and the component disposed on the substrate of the circuit module constitute a capacitor together with the resin serving as a dielectric existing therebetween.